The Anaesthetic Machine Flashcards
(96 cards)
1
Q
The advantage of having air-oxygen mixtures
A
May reduce the development of absorption atelectasis
2
Q
Reasons nitrous oxide is being less frequently used in veterinary practice
A
Concerns over its environmental impact and destruction of the ozone layer
Concerns of staff safety especially pregnant women
Security issues storing a substance subject to abuse
3
Q
Colour coding for nitrous oxide in the uk
A
Blue
4
Q
Colour coding for oxygen in the UK
A
White
5
Q
Oxygen cylinders are usually made of
A
Molybdenum steel
6
Q
Storage requirements of O2 cylinders
A
Dry, well ventilated and fireproof area. Prevent exposure to extremes of heat or dampness and keep away from oil/grease/flammable materials
7
Q
Size of cylinders usually used on anaesthetic machines
A
E-sized
8
Q
Pressure of stored oxygen
A
13,700kPa
9
Q
Oxygen in cylinders stores as
A
A compressed gas
10
Q
Nitrous oxide stored as
A
A liquid with its vapour at the top of the cylinder
11
Q
Pressure of nitrous oxide stored in a cylinder
A
4400kPa
12
Q
System to ensure only the correct gas cylinder can be fitted onto an anaesthetic machine
A
Pin index system
13
Q
Must be placed between the anaesthetic machine yoke and the cylinders valve outlet
A
Book seal - a compressible sealing washer
14
Q
Badok seal
A
A compressible sealing washer placed between the anaesthetic machine yoke and the cylinders valve outlet
15
Q
Reason for cylinders to be turned on slowly
A
To prevent a rapid release of pressure which can generate heat
16
Q
A means of connecting high pressure cylinders containing medical gases to the anaesthetic machine
A
Pin index safety system
17
Q
Stores oxygen in liquid form
A
Vacuum insulated evaporator
18
Q
Temperature range of a vacuum insulated evaporator
A
-150ºc to -170ºc
19
Q
Pressure of a vacuum insulated evaporator
A
500-1000kPa
20
Q
Where should a vacuum insulated evaporator be stored and why?
A
Away from hospital buildings due to being a fire hazard and with vehicle access for refilling
21
Q
Risk associated with refilling and VIE
A
Burns, frostbite and hypothermia
22
Q
Maximum concentration of oxygen made by an oxygen generator
A
95%
23
Q
How does and oxygen generator work?
A
Uses zeolite molecular sieves to retain nitrogen and other components of air to produce high concentrations of oxygen
24
Q
Dangers of using oxygen generators with circle circuits
A
If using very low flow rates there could be a build up or argon which is not removed buy the zeolite molecular sieve
25
Pressure of oxygen in piped oxygen outlets
400kPa
26
Schraeder probe
A unique collar indexing system and a diameter that fits into the pipelines terminal outlet for that specific gas only
27
Pressure regulator position
Between the cylinder and the rest of the anaesthetic machine
28
Pressure of oxygen after passing through the pressure regulator
400kPa
29
Pressure of oxygen inside the cylinder
13700kPa
30
Oxygen pressure from the flow control valves
1-8kPa
31
Flow rate of oxygen when flush button is used
30-70l/min
32
Pressure of oxygen when flush button is pressed
400kPa
33
Features of the anaesthetic machine that prevent delivery of a hypoxic mixture
Oxygen fail safe
Oxygen failure alarm
Hypoxic guard
34
Oxygen fail safe
Curs off delivery of nitrous oxide when oxygen pressure and flow falls
35
Oxygen failure alarm
An audible alarm to alert the anaesthetist that the oxygen supply has failed
36
Hypoxic guard
An interlocked oxygen and nitrous oxide flow controls preventing accidental delivery of a hypoxic gas mixture - ratio of oxygen to to nitrous oxide cannot be decreased below 1:4
37
Part of the anaesthetic machine that reduces the pressure of oxygen from 13700kPa to 400kPa
Pressure regulator
38
THe function of the oxygen fail safe
To cut out nitrous oxide in the event of oxygen failure
39
The main reason for nitrous oxide being used less in veterinary practice
Environmental concerns
40
Sits on the back bar of the anaesthetic machine, downstream from the flow meters
The vaporiser
41
Methods to reduce spillage and ensure the correct agent is used when filling a vaporiser
Key-fill system
42
Key fill system
Systems with groves and shapes that only fir specific bottles to vaporisers
43
vaporiser “Tec” number
Classification of more modern vaporisers, designed more recently with improved safety features. The higher the number the the better the features.
44
Tec numbers for vaporisers used in practice
3 to 7
45
How gas passes through a plenum type vaporiser
“Pushed” through under positive pressure from the fresh gas flow into a plenum (pressurised) vaporiser.
46
How gas passes through a draw-over vaporiser
Pulled over an open jar type vaporiser
47
Most common type of vaporiser
Plenum type
48
Chambers on a plenum type vaporiser
vaporising chamber where the carrier gas becomes fully saturated with anaesthetic Vapour
A bypass chamber which does not have any anaesthetic agent in it
49
Mechanisms to ensure constant ambient temperature in vaporiser
Manufactured from copper and brass which acts like a heat sink
Temperature compensation mechanism
50
Temperature compensation mechanism
A bimetallic strip and valve that alters the proportion of gas entering the vaporisation chamber depending on the temperature
51
Action of a bimetallic strip
2 different metals fused together. One side will expand at a high temperature causing the strip to bend and close a valve, the other side will constrict at low temperatures pulling the metal away and opening the valve
52
How does fresh gas flow rate affect the vaporiser output?
By either altering the proportion of the total gas flow that passes though the vaporisation chamber or by altering the efficiency and the vaporisation if the gas is coming too quickly to make contact and pick up vapour molecules
53
Effects of tiling the vaporiser
Can lead to inhalant anaesthetic entering the bypass chamber meaning that gas that is usually free of anaesthetic will become saturates resulting in high percentage of volatile agent delivery
54
Most common type of vaporiser used in practice
Plenum
55
Used to increase the surface area for fresh gas flow to pick up vapour
Wicks and baffles
56
Why is reliable administration of desflurane difficult?
It has a boiling point close to room temperature
57
Advantages of electronically controlled vaporisers
Requires virtually no servicing, can be tilted and are very accurate
58
Function of the non-return valve
Prevent damage to the vaporiser and flow meter in the event of back pressure through the system
59
Common gas outlet
Where all anaesthetic gases are delivered to the patients, connect the machine to the breathing system
60
Location of the oxygen analyser
Places between the common gas outlet and the breathing system
61
Flow rate of oxygen from emergency flush
35-75l/min
62
Pressure of oxygen from emergency flush
400kPa
63
Effects of excessive exposure to anaesthetic waste gas
Negative effects on reproductive, hepatic and renal systems. Increase the risk of haematological malignancy. Decrease the mental performance of theatre staff
64
How should a charcoal canister be positioned?
On a flat surface, below the level of the patient or APL valve, away from a heat source
65
Function of an air break on active scavenging
Draws in room air from below where the scavenging attaches. Prevents negative pressure (suction) and the buildup of pressure in the event that suction is inadequate
66
Why should vaporisers not be tilted?
Anaesthetic agent may enter the bypass chamber
67
Which part of the anaesthetic machine is designed to protect the vaporiser and flow meters from high back pressure in the back bar of the machine?
Non-return pressure relief safety valve
68
What does a charcoal canister absorb in a passive scavenging system
Violative agents - isoflurane and sevofurane
69
Additional checks needed on circle circuit
Check unidirectional valves are working and not stuck
70
How to check the unidirectional valves on a circle circuits
Close the APL valve and occlude the end of the breathing tube, squeeze the bag and visualise the valves opening and closing
71
Signs the APL valve has been left closed
Reservoir bag distended
Reduced thoracic movement and low ETCO2
Possibly leaking around the ET tube
Tachycardia and possibly drop ins spO2
72
Signs associated with increased resistance in a breathing system
Decreased tidal volume
Hypoxia
A light plane of anaesthesia due to reduced alveolar ventilation
Hypoventilation and hypercapnia - increased end tidal CO2
Altered respiratory rate - low or occasionally fast
Altered respiratory pattern - paradoxical ventilation or increased effort
73
Apparatus dead space
Dead Space beyond the patients anatomical dead space
74
PaCO2
Partial pressure of carbon dioxide
75
Affect of increasing the dead space to tidal volume ratio in small animals
May increase the work of breathing as the volume needs to increase to maintain PaCO2
If animal cannot cope then PaCO2 will rise
76
External landmarks for pre-measuring ET tubes
Point of the shoulder to incisor arcade
77
Charcoal passive scavenging systems must not be used
when nitrous oxide is being delivered to the patient.
78
Filter used in an oxygen generator to remove nitrogen and other components from air to produce oxygen
Zeolite molecular sieve
79
Ratio of oxygen to nitrous oxide
1:4
80
VIE stands for
Vacuum insulated evaporator
81
Accuracy of a conventional flowmeter
+/- 2.5%
82
In a machine capable of administering more than one gas, where is the oxygen flow control knob located?
Far left of the bank
83
baffling the oxygen tube
Where oxygen is the last gas to be added to the fresh gas flow despite being on the left of the machine
84
Why should oxygen be the last gas added to the fresh gas flow?
To prevent delivery of a hypoxia mixture in the event of leaks within the tubes (less O2 being delivered than expected)
85
Features to ensure that the oxygen flow meter can be easily located
Flow control knob protrudes further than others and had a coarsely fluted profile
The names of gases are written on the knobs
The back of the tubes are fluorescent so they glow in the dark in the event of a power cut
86
Function of an air intake valve
To allow room air to be taken in by the anaesthetic machine in the event of oxygen failure
87
How does the hypoxic guard work?
Reduces the flow of nitrous oxide being delivered when the flow of oxygen is reduced keeping the ratio at or above 1:4 (25% oxygen)
88
High resistance vaporiser that sits outside of the breathing system (VOC)
Plenum type vaporiser
89
Low resistance in-circuit vaporiser
draw-over vaporiser
90
How does a plenum type vaporiser work?
Fresh gas is split into 2 streams as it enters the vaporiser, 1 stream enters the vaporising chamber and becomes fully saturated with volatile agent while the other bypasses the vaporising chamber and remains free of volatile agent, the two streams combine before leaving the vaporiser
91
How does the dial on the vaporiser affect the flow of gas through the vaporiser?
The percentage dial changes how much of the carrier gas is directed into the vaporising chamber and how much is bypasses
I.e 2% of the oxygen flow rate is directed into the vaporising chamber to become fully saturated
92
Function of the pressure relief valve
Opens when pressure in the back bar reaches 30-40kPa
93
Why should a charcoal scavenging canister be placed in a flat surface?
To allow the expired CO2 to flow from the bottom vents
94
Why should vaporisers not be tilted?
Anaesthetic gas may enter the bypass chamber
95
Which part of the anaesthetic machine is designed to protect the vaporisers and flow meters from high back pressure in the back bar of the machine?
Non-return pressure relief safety valve
96
What does a charcoal canister absorb in a passive scavenging system?
Volatile agents eg isoflurane and sevoflurane
